The present invention relates generally to x-ray generating devices, and more particularly, to an improved x-ray generating device having optimized record technique selection.
Fluoroscopy generally provides a real-time imaging mode for various x-ray procedures. Current radiography and fluoroscopy systems (R&F) include two independent exposure applications, record and fluoro. A user may adjust the initial tube peak voltage (kVp) in fluoro applications and set both tube voltage (kVp) and tube current (mA) in record applications. These initial values are set based on user preference or default values from a saved protocol database.
During a fluoro exposure, the tube current (mA) is adjusted first until a tube or patient dose limit is reached. Tube voltage (kVp) is then increased if necessary until proper image brightness (dose) is achieved. This sequence is repeated at the start of each fluoro exposure.
There are several parameters, which are controlled in order to effectively regulate exposure. These include kVp, mA, pulse width (exposure time), image quantum noise level (i.e., image receptor entrance exposure or entrance exposure rate). These also include focal spot, x-ray beam spectral quality and patient entrance radiation exposure rate (or Air Kerma). Each of these parameters has an optimal setting, which is unique for each of the procedure demands and patient sizes encountered.
During a record exposure, for example, the system may achieve proper brightness (dose) by applying the predefined tube voltage and tube current and increasing exposure time until the photocell reaches the desired brightness or until a time limit (backup time) is reached. Reaching backup time results in exposure termination and possible dark images. Any predefined record technique is based strictly on experience of the user.
Current procedures include the fluoroscopic sequence as a means of positioning a recording device through visualization of the internal anatomy of a patient. The recording device is then presented with the same view as in the fluoro mode, resulting in framed images prepared for diagnosis. This type of procedure generally requires a minimal amount of fluoroscopic time, which is typically less than five minutes.
Other procedures use the fluoroscopic mode as the primary mode for positioning instruments within the body, conducting medical intervention, and performing a medical diagnosis of a patient based on the fluoroscopic images. These procedures can be very lengthy and require a lengthy exposure to x-ray radiation.
There is currently no method for determining the current patient thickness and for the record technique and frame rate selected if an exposure will result in a backup time being reached. Additionally, no thermal prediction is possible based on an estimated exposure time. Any current prediction is based on the technique selected by the user and the maximum exposure time (backup time). This severely limits the exposure sequence because most exposures are actually less than the backup time.
It is generally desirable to improve the efficiency and performance of an x-ray generating device and to optimize exposures. Additionally, it is desirable to choose optimal techniques based on patient thickness and contrast being used.